Waiting for the key to turn in the door; glancing longingly at the empty space at the table; leafing through well thumbed photographs at images frozen in time.

These are some of the actions carried out by families of the long term missing.

Every 90 seconds, someone goes missing in the UK. Annually, around 180,000 people are reported missing.

And while most people are found within the first 48 hours, around 3,600 people stay missing for weeks, or even longer. For families waiting for long periods of time for news of a loved one, the UK’s leading missing persons charity says Christmas is particularly difficult.

After a week, the likelihood of finding a person decreases drastically. Georgia Romeril works at Missing People, a national charity dedicated to reuniting families. “Any moment which involve families getting together draws attention to the fact someone is not there,” she says.

Missing People supports families and appeals for many of the long-term missing. Their oldest missing case is of Mary Flanigan who disappeared in 1959. The east London teenager set off for work on New Year’s Eve 1959 at the Tate and Lyle sugar refinery, but she never returned.

Growing anxious on New Year’s Day, her family went to the factory and were shocked to discover she hadn’t been to work for two weeks, despite setting off to go there each day.

Fifty-nine years later, it is still unknown what happened to the 16-year-old. Her parents Mary and Barry have since died without ever finding out.

Romeril says that families describe the lack of answers as the most difficult part of the ordeal. “Having a missing person is very different to having someone pass away, which gives people the opportunity to go through the grieving process and move on,” she said.

“Never having answers means there is no process to go through. It is described as ‘ambiguous loss’ as the person is physically absent yet psychologically present.

“It is the difference between grieving the loss of a person and the loss of a person who might still be out there.”

HuffPost UK spoke to three families preparing for another Christmas without their missing loved ones. 

Simon: “Every Christmas we hope he’ll return” 

Whenever Rachel Pickthall goes on an escalator, she imagines her brother Simon Hodgson-Greaves going past.

“I dream about Simon and look for him all the time” the 51-year-old says. “I’m trying not to let it become an obsession but until you can show me his body, I cannot possibly give up hope he is somewhere out there.”

Simon was reported missing on December 21, 2013 at the age of 48 when his camper van was found in a car park at Bempton Cliffs, North Yorkshire.

“Simon had a bit of a reputation for wandering off and disappearing from our lives for a bit and then just turning up again,” Rachel said. “But on this occasion, the car park attendant contacted the police after finding Simon’s camper van abandoned there, as the cliffs are a notorious suicide spot.”

Rachel admits her brother did have some mental health issues but says the family and police felt his behaviour leading up to that day did not suggest he was going to take his own life, and there was no suicide note.

“The police did a really good job of looking for Simon with land and sea rescue and searching the rocks. There were lots of sightings of him in various places – but none were corroborated with CCTV.

“But equally, Simon’s body wasn’t found either.”

Rachel describes Simon as an extrovert who lived his life in an unpredictable way. “For the first couple of years, we told ourselves Simon would just walk through the door one day.” she said. “Time doesn’t heal. We still don’t know where Simon is and he hasn’t turned up on our doorstep.”

Rachel and her two sisters are desperate to know what happened to their brother – particularly for the sake of their 78-year-old mum. “I would sell my soul to find out what happened to Simon,” says Rachel. “I just want to know he is safe. He doesn’t have to come back into the family if he doesn’t want to.”

Describing the anguish of “ambiguous loss”, she says: “It is like you have lost someone but you have not buried or cremated them or said your goodbyes.”

As Simon’s birthday is just before Christmas, this time of year is particularly emotional. “A couple of times in the past, when Simon disappeared for periods of time, he suddenly turned up again at Christmas.

“Every year, we hope this will be the Christmas when Simon comes back. I will never give up looking for him.”

Fatima: “She made me my breakfast – then I never saw her again” 

It was an ordinary Friday morning in February 2016 when Mohamed Mohamed-Ali was woken up for work by his wife, Fatima, telling him his breakfast was ready.

As he left the house, Mohamed asked if she needed any bread and milk. She replied to say she would go shopping the following day.

It was the last conversation they had. When Mohamed returned home from work, his 52-year-old wife had disappeared.

The father-of-three told HuffPost UK his wife never usually left the house on Fridays. As a devout Muslim, she did her prayers. “As soon as I arrived back home, I knew something wasn’t right as Fatima wasn’t there and her car keys were on the table.”

Mohamed, now 59, who lives in the village of Denton, East Sussex, walked to the local hairdressers in case his wife was there. He frantically called her mobile – only to hear it ringing in the bedroom.

Realising she had left the house without her handbag, keys and mobile phone, he alerted the police.

Almost three years later, Mohamed’s wife of 36 years has still not been found, and he admits he has battled suicidal thoughts.

The couple married in Tanzania when Mohamed was 23 and Fatima had just turned 18. “I knew her since she was a little girl and we grew up together. I never thought I’d end up married to such a beautiful lady.”

Soon after their wedding, the couple settled in the UK and went on to have two daughters and a son, followed by four grandchildren.

“Fatima was devoted to her family and was a perfect wife, mother and grandmother.

“Her disappearance was so sudden and is a complete mystery. I cannot understand how someone can just disappear in this day and age from a small island.”

Police found Fatima’s disappearance out of character and carried out extensive enquiries, scouring the area with a police helicopter and checking CCTV.

Mohamed said: “My world fell apart on that day and I felt devastated and panicked – and still do.

“Fatima did everything for me and I was very grateful. I am not coping well without her and don’t know where anything is at home.

“I’ve had suicidal thoughts go through my head but I know I have to survive for my children. We both worked so hard to have a house, bring up our children and put them through university. Now it should have been our time of life but she is not here.”

He added: “This is one of the worst times of year as Fatima loved Christmas and we had all the family round with food, presents and a Christmas tree.

“Even though she believed in her own religion, Fatima respected every religion and celebrated Christmas, Diwali and everything.

“We are a normal, simple family but something like this can happen to anyone. We just want her back home.”

Paul: “He was my brother and my friend”

While social media revelled in the photo from Blackpool police appealing for a beer thief who was a dead ringer for Ross from the hit 90s sitcom Friends, Zoe Tweddle felt a jolt of recognition.

“I was convinced it was my brother Paul who has been missing for 11 years,” the 34-year-old from Cumbria said.

“It looked uncannily like him – his hair, his appearance, the way he was standing, the look in his eyes.

“It took my breath away and I thought: ‘That could really be my brother.’”

Zoe and Paul’s foster parents contacted the police but the suspected thief turned out to be someone else, not Paul Trowbridge, who would now be 36.

However, Zoe says the incident has given her renewed motivation and vigour to find her brother. 

The siblings had a rocky start in life and ended up being separated in the care system. “Our parents both had severe mental health issues and met at an outpatients mental health facility, fell in love and got married. 

“By the time I was four, Paul and I were both in the care system but in separate places. We were allowed to keep in contact but it wasn’t the same. We did not grow up together as siblings but we still had a brother-sister relationship.”

Zoe said: “Paul inherited our parents’ mental health issues and they became apparent during his teenage years.

“He developed severe mental health issues and was diagnosed with schizophrenia. He also made a few silly choices with life and fell into petty crime and was a bit of a lovable rogue.”

By the time of his disappearance, Paul had not been taking his medication and was not regular touch with his foster family or his sister.

He was reported missing after disappearing soon after packing for a holiday to Barbados. Since then, there have been no sightings or activity on his bank account.

Zoe told HuffPost UK: “I feel an awful lot of guilt that Paul had mental health issues. We both had a troubled start in life. But since being adopted, I’ve had a brilliant life with a really nice family.”

Tweddle, who is married and expecting her first child added: “I am happy and I just wanted that for Paul as well. He was very close to his foster family and they miss him so much too.

“Like everyone, we laughed at the spoof David Schwimmer video – but thinking it was Paul also re-opened the wounds.

“I hope he is alive and well and just want to know he is OK.

“Christmas is a particularly difficult time as it is a time of togetherness and it hits home how much Paul has missed out on everyone’s lives.

There are cases of missing people being found after many years, but Romeril from Missing People warns it isn’t always a happy ending. “We know of people who have been found after weeks or years, which is brilliant news,” she said.

“But quite often, it is not the end of the journey as whatever the reason for the person going missing can still be there when they return.

“In some circumstances, there may still be issues to address. But with the right support, it can be the beginning of a happy ending.”

If you have any information about any of these missing people or are missing and want to send a message to your family, call or text Missing People on: 116 000 or e-mail: 116000@missingpeople.org.uk